A quartz boat used as a carrier to support wafers is useful in many processes where a high temperature environment is involved. For instance, in a dry/wet etching process or a thermal treatment process, the wafers are held up by the quartz boat, and then transferred to a chamber or a furnace for further processing. Conventionally the body of the quartz boat 10, as shown in FIG. 1(a), includes the following elements.
(1) A front quartz plate 61.
(2) A rear quartz plate 62.
(3) A first pair of quartz rods 63 are disposed longitudinally to connect the front quartz plate 61 and rear quartz plate 62 at an upper location respectively.
(4) A second pair of quartz rods 64 are disposed longitudinally to connect the front quartz plate 61 and rear quartz plate 62 at a lower location respectively. A welding operation is further performed on connections 65 located between the second pair of quartz rods 64, and the front quartz plate 61, and rear quartz plate 62 respectively.
(5) A third pair of quartz rods 66 are disposed substantially vertically to connect to the first pair of quartz rods 63 and second pair of quartz rods 64 at center locations of them respectively.
(6) A fourth quartz rod 68 is disposed horizontally to connect the second pair of quartz rods 64 at center locations thereof respectively.
(7) A plurality of slots 70 cut on the surface of the first pair of quartz rods 63 are provided to accommodate the wafers.
As illustrated in FIG. 1(b), in the conventional approach, each of the second pair of quartz rods 64 is connected to the rear quartz plates 62 at connection 65 by welding respectively. When the dry etching process is performed, it is noted that the quartz boat 10 is subjected to a large temperature-transition environment, for example, an environment of temperature transition varying from 180.degree. C. to 25.degree. C. Thus, the strength of the quartz boat 10 at the connections 65 becomes weaker due to such a large temperature transition. In addition, it is observed that the quartz boat 10 is accessed frequently during operation of the dry etching process. In other words, a portion of the quartz boat 10, especially at the connections 65, is subjected to an unavoidably local vibration. This leads to potential damage to the strength especially at the connections 65 of the quartz boat 10. Thus, it is possible that the quartz boat 10 tends to be more easily fragmented and becomes fatigued under the above-mentioned environment. Therefore, it is desirable to enhance the strength of the connections 65, such that the lifetime and reliability of the quartz boat 10 can be increased.
The main object of the instant invention is to provide a cost effective solution to enhance the strength of the quartz boat 10 at the connections between the quartz plates and quartz rods of the quartz boat.